1. Field of the Invention
The present invention relates to power electronic components, and more particularly to semiconductor chips soldered between two flat heat sinks, generally copper disks.
2. Discussion of the Related Art
FIG. 1 is a partial cross-sectional view of a device for mounting a chip between two disk-shaped heat sinks. The device 10 includes cylindric cavities 12 (one of which is shown) in which are successively introduced a first copper disk 14, a chip 15 (generally square-shaped), and a second disk 16. The diameters of disks 14 and 16 are larger than a diagonal length of chip 15. Chip 15 is shown as viewed laterally along a diagonal length.
Elements 14-16 are interconnected by means of solder 18 initially deposited on both sides of chip 15 and/or on one surface of the disks. One can also use solder preforms between each face of the chip and the corresponding disk.
The diameter of cavity 12 is slightly larger than the diameter of disks 14 and 16 providing easy insertion and removal of the sandwich formed by elements 14-16. Thus, in most cases, as represented, elements 14-16 are disposed in a stepped position and a corner of chip 15 (the right corner in FIG. 1) can protrude from one of the heat sinks and be further subject to shocks capable of damaging it. Additionally, in order to melt solder 18, the device 10, provided with sandwiched elements, is introduced into an oven by a conveyor. If elements 14-16 happen to be initially suitably aligned, the vibrations of the conveyor tend to misalign them, this shifting being increased by the molten solder 18.
An object of the invention is to provide a device for positioning two heat sinks with respect to a chip so as to prevent a corner of the chip from protruding from the heat sinks.
Another object of the invention is to provide such a device on which the chips and heat sinks can easily be disposed.
A further object of the invention is to provide such a device allowing the use of square-shaped heat sinks.
Those objects are achieved by using, instead of the above-mentioned cavities, stops in which the sandwiched elements are positioned due to gravity, an adequately sized stop portion being combined with each element of the sandwich.
In conventional systems, it is not possible to position the elements by using gravity, for example, by tilting device 10, because two corners of the chips are then positioned flush with the edge of the heat sinks and are not protected from shocks. According to the invention, by suitably disposing the stop portions respectively associated with the elements of the sandwich, the corners of the chip will always be set back with respect to the edges of the heat sinks.